Abrasive article



W G. W. CHORMANN ET AL ZWJ ABRAS IVE ARTI CLE Filed May 31, 1933 INVENTOR. GEORGE W. CHORMANN FREDERICK A. UPPER BOYD H. WORK ATTORNEY.

Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE ABRASIVE ARTICLE Application May 31, 1933, Serial No. 673.654 1': Claims. (in. 51-207) of the kind that-is used in connection with a series of centerless'grinders. Such a regulating wheel has to be mounted with great care on its shaft or spindle. In the past it has been customary to form an arbor hole bushing of lead,

babbitt, or other soft material which is low melting and can be readily cast in place. This type of bushing is ordinarily too plastic to maintain an accurate shape under large and prolonged stresses; and in changing a wheel from one shaft to another, a bushing of soft metal may also be deformed by contact with the threads on the shaft. The casting of a strong, high melting metal into the arbor hole of the wheel is, of course, im-

practical.

In molding abrasive wheels it is necessary to use a mold center or core having a taper so that the center of the mold can bekremoved without damaging the freshly molded article. Removing the mold center leaves a tapered hole in the fresh- 1y molded wheel which necessitates finishing the hole to the proper dimensions. If the finished wheel is mounted on the machine spindle so that the abrasive is in direct contact with the shaft, the latter is injured by the abrasive contact, especially under the varying stresses caused by change of speed and by the variation in pressure upon the periphery of the wheel. A metallic bushing is thusnecessary in order to provide a satisfactory contacting surface with the spindle. A cast bushing is. not only subject to deformation during use, but it requires individual adjustment of each wheel on its spindle, and this adjustment requires considerable time and care on the part of the workman.

According to our invention, it is possible to mold wheels of any practicable thickness and provide the same with mountings having bearing surfaces of such a character that there is no substantial deformation during use. Our improved mounting preferably takes the form of a series of inserts extending into the arbor holeof the wheel and adapted to engage with the contacting portion of the shaft. These mountings may be inserts of steel, brass, phenolic condensation product in its infusible, inalterable state (known as C stage), or other strong, enduring material, and can be inserted into the wheel during the molding operation and retained in situ during the curing of the abrasive bond. The portion ofthe wheel between the inserts does not 5 necessarily contact with the spindle, and consequently can be molded with the usual taper and need not be subjected to any further finishing operation. I

A desirable method of making our abrasive wheel comprises using a tapered mold center which is slightly larger than the spindle on which the wheel is to be mounted, and cutting straight slots in the mold center or core to receive the mounting inserts. The inserts can thus be placed in the slots and the wheel molded around the core. The inserts can be readily removed from the slots in the mold center, but will be retained within the body of the abrasive wheel.

, The nature of our improved abrasive wheel can be ascertained from the annexed drawing, in which:

Figure 1 shows a central section of such a wheel, the section being takenin a plane perpendicular to the axis;

Figure 2 illustrates a composite abrasive wheel made up of members similar to that shown in Figure 1; and

Figure 3 is a fragmentary view containing a transverse section of a portion of a wheel and illustrating amodiflcation of the wheel mounting shown in Fig. 1.

The abrasive wheel 2 is shown as having metal inserts 3' which can be inserted as a preliminary to the molding process and retained within the wheel during curing. When this method is used the inserts can be placed in slots in the core during the molding process and the abrasive mix packed around the core and the projecting metal pieces. After subjecting the mix to pressure in the mold, the core may be removed and the molded article cured with the inserts in situ. If desired, the article can also be cured on the core. In either case the inserts can be machined to compensate for shrinkage of the article during the cure. As the greatest accuracy canbe obtained by grinding, lapping or honing, we prefer to machine to size by these methods. Other suitable methods of machining, such as broaching or reaming, may be used, and highly accurate flnishing to dimensions accomplished.

We may use brass, for example, as the material for the inserts, fused alumina as the abrasive grain, and rubber as the bonding constituent of the mix. The molded article should heated to a temperature sufficiently high to vulcanize the rubber in accordance with the usual methods of curing abrasive articles of this nature. Upon completion of the curing operation, the inserts will be found to be firmly embedded in the abrasive body.

After the wheel has been cured it is mounted on a shaft 6, and the wheel can be dressed to size if necessary with a. diamond tool or other suitable dressing means.

Our improved wheel has a number of advantages which may be briefly referred to as follows:

1. The core and the slots therein can be made with great precision, and the inserts can be made with equal precision. By tamping and pressing the mix around the core in the mold, with the inserts projecting from the core into the mix, the inserts can be placed very exactly in the molded article. The labor and expense connected with finishing the wheel and bushing the arbor hole are greatly reduced.

2. The wheel arbor contact, being non-abrasive, does not wear the spindle upon which it is mounted. A metal to metal contact, or in general a contact between highly finished surfaces, makes the mounting of the wheel easier and makes practical further the mounting of a wheel with a hole size more nearly approaching the size of the shaft on which the wheel is to be mounted.

3. A better fit and more accurate centering of the wheel is obtained by using a limited number of contact points as, for example, three contacts which can be accurately finished, than when an attempt is made to have the complete surface of the arbor hole of the wheel in contact with the spindle.

4. By machining the inserts, an arbor hole can be formed of standard dimensions, so that a series of feed or regulating wheels can be mounted interchangeably on similar shafts of similar grinding machines. The term machining may include broaching, reaming, grinding, honing, lapping and burnishing.

5. A composite wheel can be built on a given shaft 8, as shown in Figure 2, since each individual wheel 9 is molded in the same manner and is provided with inserts 3' of the same dimensions and having substantially the same relative position in each of the individual wheels. Composite wheels have been built up between terminal driving flanges, the intermediate members being driven by contact with adjacent members. In such composite wheels the pressures exerted by the terminal driving flanges are large and may cause rupture of the wheel under stress. Our improved composite wheels are driven by torque exerted by the shaft in a similar manner on each of the individual wheels.

In view of the tendency of some organically bonded wheels to distort under great stress, it is desirable to have the torque transmitted by means of a plurality of keys which are firmly anchored in the interior of the abrasive wheel.

In addition to the advantages specifically enumerated, it will be noted that the inserts 3 not only act as centering devices on the shaft 6, but act as driving keys between the shaft and the abrasive annulus 2. Driving flanges are, therefore, unnecessary in the mounting of our improved wheels.

The torque may be transmitted directly from the shaft to the inserts, or keys may be inserted between the shaft and the inserts which are rooted in the abrasive wheel, grooves or slots being made in both the shaft and in the insert for receiving such keys. The last mentioned form of mounting is illustrated in Fig. 3 where torque is transmitted from the shaft 6 by means of keys I to inserts 3' and thence to the abrasive annulus 2.

While rubber bonds have been specifically mentioned and have proved satisfactory in our manufacturing processes for our improved wheels, any bond which willpermit the curing of the wheel while the inserts are positioned therein can be used.

The method of molding the abrasive article around the inserts and curing of the wheel with the inserts in place is very desirable and possesses a number of advantages over other methods of positioning the inserts within the wheel. It is possible, however, to position these inserts into previously formed slots in the wheel by cementing the inserts to the abrasive, or by other suitable means.

We claim:

1. An abrasive wheel containing an arbor hole, and a plurality of hard metal inserts embedded in the wheel and extending within said arbor hole, the said inserts being adapted to accurately engage with a drive shaft.

2. An abrasive device comprising an abrasive annulus and hard metal inserts projecting into the arbor hole of said annulus, the abrasive being molded about the inserts and the inserts be- :1

ing shaped to act as centering devices on a shaft for driving the annulus.

3. An abrasive device comprising an abrasive annulus and hard metal inserts projecting into the arbor hole, and a driving shaft provided with 3 a plurality of slots arranged parallel to the axis and distributed at uniform angular intervals, said inserts being shaped to enter said slots in the driving shaft whereby torque is transmitted from the shaft tothe annulus at a plurality of points.

4. A composite abrasive wheel composed of a plurality of individual members in which each member is formed with a plurality of hard metal inserts of similar shape and similarly placed with respect to the arbor hole of each wheel whereby torque is transmitted in a similar manner from a single shaft to each of the component members of the composite wheel.

5. An abrasive device comprising an abrasive annulus and hard metal inserts projecting into the arbor hole of said annulus, and a driving shaft provided with a plurality of slots arranged parallel to the axis and distributed at uniform angular intervals the abrasive being molded about i the inserts and the inserts being subsequently machined and polished to fit accurately in said slots.

6. An abrasive device comprising a driving shaft, an abrasive annulus to be driven by said shaft, hard metal inserts projecting into the arbor hole of said annulus, the abrasive being molded integrally with the inserts, and torque transmitting keys inserted in complementary slots in the inserts and in said driving shaft respectively.

7. In an abrasive wheel provided with an arbor hole, three lands located in the said arbor hole and adapted to engage less than one-half the periphery of a drive shaft and accurately posiand adapted to engage a drive shaft and accurately position the said abrasive wheel thereon.

9. In an abrasive wheel provided with an arbor hole, a plurality of lands of hard machinable material comprising root portions molded in the abrasive wheel and projections extending into the said arbor hole, said projections. being machined and polished to fit accurately on a drive shaft and accurately position the said abrasive wheel on the said drive shaft.

10. In an abrasive wheel construction, an arbor provided with a plurality of longitudinal slots, an abrasive wheel provided with an arbor hole and mounted on the said arbor, and a plurality of lands located in the said arbor hole and engaging the said arbor in the said longitudinal slots to accurately position the said abrasive wheel thereon, the said lands including all points of contact between the said wheel and the.

said arbor.

11. In an abrasive wheel construction an arbor provided with a plurality of longitudinal slots, an annulus of bonded abrasive material provided on its inner surface with a number of longitudinally extending slots equal to the number of slots on the said arbor and mounted on the said arbor whereby each slot in the said arbor is opposite a slot in the said abrasive wheel and portions of internally strong material occupying the channels formed by each pair of opposite slots to accurately position the said annulus of abrasive material on said arbor and permit the application of torque to the said annulus by the said arbor, the said annulus and the said arbor being out of contact with each other except through the medium of the said portions.

12. In an abrasive wheel provided with a cylindrical arbor hole, a plurality of portions of hard machinable material embedded in the abrasive material adjacent the arbor hole and extending longitudinally therein, the said portions extending to a uniform height above the surface of the said arbor hole.

13. in an abrasive wheel provided with an arbor hole, a plurality of brass inserts embedded in the abrasive material adjacent the said arbor hole, and extending longitudinally therein, the said inserts extending above the surface of the said arbor hole and being machined and polished to fit on a driving shaft.

14. In an abrasive wheel provided with an arbor hole, a plurality of hard im'usible resin inserts embedded in the abrasive material adjacent the said arbor hole and extending longitudinally therein, the said inserts extending above the surface of the said arbor hole and being machined and polished to fit on a driving shaft.

15. In an abrasive wheel provided with an arbor hole, a plurality of steel inserts embedded in the abrasive material adjacent the said arbor hole and extending longitudinally therein, thesaid inserts extending above the surface of the said arbor hole and being machined and polished to fit on a driving shaft.

16. An abrasive wheel comprising an abrasive annulus formed of abrasive particles bonded together by means of a tough hardened organic bond, and hard metal inserts rigidly attached to the abrasive wheel by the hardening of the bond but projecting into the arbor hole of the wheel, said metal inserts being widely separated units which have been machined subsequently to the hardening of the bond so that they fit accurately in grooves in a driving shaft, the machined areas being concentric with the axis of the wheel.

17. A composite abrasive wheel comprising a plurality of abrasive annuli each having a plurality of hard metal inserts united with the abrasive but projecting into the arbor hole and machined so that the inserts projecting into the arbor hole of each annulus fit into corresponding grooves on a driving shaft, and means for pressing the annuli into close contact with each other while they are drivingly connected to the shaft,

40 whereby an abrasive wheel of desired length is built up on a shaft of corresponding dimensions.

GEORGE W. CHOR FREDERICK A. UPPER. BOYD H. W0. Y 

